1. Field of the Invention
The present invention relates to the technical field of regulating devices and, more particularly, to a safe electric power regulating circuit for regulating an input voltage to perform voltage buck or boost.
2. Description of Related Art
Power batteries are commonly used as power source for electric vehicles, such as electric bicycles, electric motorcycles, and electric automobiles. A typical power battery has a voltage approximately three to four volts. But according to the type of output power of the motor, the electrical vehicle generally requires a power source of 48-72, 72-200, or 300-700 volts. Accordingly, if power batteries are used as the power source of a motor, the voltage supplied by the power batteries has to be enhanced to exceed the voltage required by the motor.
Currently, a series of tens or hundreds of power batteries are connected to provide high-voltage power for a motor, and a power management circuit is used to control individual battery. When the power of any one of the power batteries is insufficient, the power management circuit disconnects this battery to avoid failure from over-discharging. However, the cost of such power management circuit is very high. To overcome this, a voltage boost circuit is required to enhance the battery voltage up to the required voltage.
FIG. 1 is a circuit diagram of a typical voltage boost circuit. As shown in FIG. 1, the typical voltage boost circuit is comprised of an inductor 91, a switch 92, a diode 93, and a capacitor 94. The switch 92 is controlled to be on in order to make the inductor 91 to ground to generate a large current I to the inductor 91. If the switch 92 is controlled to be off, it will make the inductor 91 to transfer energy of ½LI2 to the capacitor 94, where L indicates the inductance of the inductor 91.
In practical application, as soon as the current generated by shorted circuit reaches a required magnitude, the switch 92 has to be turned off to avoid the circuit damage from danger caused by over-current. Typically, the energy transfer can be adjusted by controlling the turning-on time of the switch. However, the current generated in such a way increased exponentially in a short period of time, and the transferred energy increased in proportion to a square of the generated current. Therefore, when the control signal of the switch is interfered by low frequency noises, the turning-on time may be too long, resulting in an over-current which causes damages to the entire circuit and makes the electric vehicles to become dangerous.
Therefore, it is desirable to provide an improved safe electric power regulating circuit to mitigate and/or obviate the aforementioned problems.